Email has enabled businesses to improve communications and share information. Used effectively, email can also help businesses to improve efficiency. Email systems have been enhanced in many ways to increase the convenience and efficiency of its use. In current email systems, users can forward emails to an individual or a group of individuals to share valuable information. However, multiple users may forward the same email to the same user. If a recipient's address happens to be in more than one distribution group (or in both the original recipient list and the forwarded group), the recipient will receive the same email multiple times. The reading of duplicated messages lowers the efficiency for the receiver.
Duplicate forwarded emails can be received in two ways: horizontal duplication and vertical/cyclic duplication. In horizontal duplication, multiple senders forward the same email to their respective distribution groups, and their distribution groups overlap. For example, John is the project manager for a project named Magic. Mary is the development manager for Magic, so she includes John in her email distribution list. John reports to Robert, therefore John is also on Robert's distribution list. There is a new development process in the company where John, Mary and Robert work. This new process is communicated to Robert and Mary through identical emails sent by their managers. When Robert and Mary forward the emails from their managers to the people who work for them, John receives two emails with identical content from Robert and Mary regarding this new process.
In vertical duplication, a recipient belongs to more than one distribution list along the email forwarding path. For example, John and Mary are members of an architectural board, and John's manager is Robert. John receives an email with an overview of a new project, and forwards the email to the rest of the architectural board. Mary receives John's email and forwards the email to Robert. Robert forwards the email to his department, which includes John. John receives the forwarded email he had forwarded himself.